A human hand generally has five fingers, namely a thumb, a forefinger, middle finger, a ring finger and a little finger respectively, in addition to the thumb having a special movement law, a movement law of other four fingers is basically the same. Each finger is divided into three knuckles, namely a base knuckle, a proximal knuckle and a distal knuckle respectively, which are connected by joints at corresponding positions, and a nail grows on the distal knuckle. For some disabled persons, a prosthetic hand is required to realize basic functions of a human hand.
Prior to 2007, the most popular prosthetic hand on the market was a single-degree-of-freedom prosthetic hand manufactured by OTTOBOCK company of Germany. The prosthetic hand has only basic opening and closing functions, and a basic working principle of the prosthetic hand is that an electromyographic signal sensor senses a movement demand of a disabled person and sends a corresponding signal to a microcontroller, the microcontroller sends a control instruction to enable a micromotor to run, and the micromotor drives a prosthetic finger to move through a mechanical transmission chain, so as to realize the opening and closing of the prosthetic hand.
With the development of multi-finger dexterous hand technology in the robot field, the research of a multi-degree-of-freedom prosthetic hand has played a great promoting role. Since 2007, many kinds of multi-degree-of-freedom prosthetic hands have been developed, the vast majority of which employ an underactuated mechanism, i.e., generally only one micro-driving motor is required for one finger, while the movements of a base finger joint (corresponding to a connecting joint between the base knuckle and a palm) and a proximal finger joint (corresponding to a connecting joint between the proximal knuckle and the base knuckle) are coupled, with one micro-driving motor driving the base knuckle and the proximal knuckle simultaneously. The mechanical transmission of the base finger joint usually adopts cable (rope) transmission, bevel gear pair transmission, worm gear pair transmission or sliding screw pair transmission, etc., while the mechanical transmission of the proximal finger joint usually adopts cable (rope) transmission, connecting rod transmission or gear pair transmission, etc. Different combinations of a base finger joint transmission chain and a proximal finger joint transmission chain can form different products. At present, there are two kinds of prosthetic hands sold more in the market, one kind of prosthetic hand using worm gear pair transmission for a finger base finger joint and cable (rope) transmission for a proximal finger joint, and the other kind of prosthetic hand using sliding screw pair transmission for a finger base finger joint and connecting rod transmission for a proximal finger joint.
A prosthetic hand has more parts, the design of the prosthetic hand involves many problems, such as how to make these parts cooperate with one another to achieve basic functions similar to a human hand, how to ensure the reliability of work, how to reduce the complexity of a structure and the difficulty of assembly, how to reduce the cost, and how to make the structure beautiful, and these problems can be divided into many specific problems. Although productization of the prosthetic hand is realized at present, the prosthetic hand still has many defects in design, such as an existing iLim prosthetic hand has a finger DC motor with a lead connected to a lead output device of a base finger joint mounting rack, and the lead output device is provided with a fixing sleeve, a sliding guide pin and a compression spring. The structure of the prosthetic hand is complex, is difficult to miniaturize, and occupies a design space, and the structure and the appearance of a finger connector of the prosthetic hand are complex, including a conductive column which is in contact with a finger sliding guide pin, and a base joint outer cover which is complex in shape.
During the development of a prosthetic hand, the inventor finds at least the following problems in the prior art:
A prosthetic finger has more base finger joint parts and a complex assembly relationship, the parts are difficult to be effectively and accurately positioned, the assembly difficulty is high, especially base finger joint structures of some existing prosthetic fingers have simple assembly structures to result in poor work reliability of the base finger joint and easy failures.
For some existing prosthetic fingers, connecting structures between base knuckles and base joints are complex, and the finger base knuckles are difficult to be assembled to a base joint structure, and cannot be assembled simply and effectively.
For some existing prosthetic fingers using cable transmission for proximal finger joints, the proximal end of a transmission rope is connected to a worm gear, but a used specific connecting structure is not convenient for assembly, and the proximal end of the transmission rope is easy to fall off, which is not conducive to the reliable use of a prosthetic hand.
For some existing prosthetic fingers, the proximal finger joints use cable transmission, frequent bending and unbending of fingers can easily make a transmission rope rub and scratch on base knuckles of the fingers, long-term use of the prosthetic fingers easily makes the transmission rope be worn and even fractured to affect the service life of a cable transmission mechanism.
For some existing prosthetic fingers, tension springs are used for connecting proximal knuckles and base knuckles of the fingers to realize automatic reset of the proximal knuckles of the fingers during unbending of the fingers, while ends of the tension springs are fixedly connected, so the tension springs are frequently under the combined action of tension and bending moment, and long-term use of the fingers will make the tension springs have bending residual deformation. Therefore, the prosthetic fingers will have bending and unbending of fingers not in place, and the use characteristics of the prosthetic fingers and prosthetic hands are reduced.
For some existing prosthetic fingers, distal knuckles and proximal knuckles of the fingers are not distinguished structurally, so that the proximal knuckles of the fingers cannot be assembled with other parts conveniently, or end face lamination is used for the proximal knuckles and the distal knuckles of the fingers, and then a connection mode with other connecting pieces for connection is used, so that the connection reliability is poor, the structure is not beautiful enough.
For an existing prosthetic finger, because of part of the structure thereof has the above problems, the whole prosthetic finger has poor work reliability, and is not easy to assemble.
Since the amount of movement of the proximal knuckle of a thumb a human is very small, the design of a prosthetic thumb may not take this movement into account. However, for some existing prosthetic thumbs, the structure between the proximal knuckle of the thumb and the base knuckle of the thumb is very different from the connecting structure between the proximal knuckle and the distal knuckle of a general prosthetic finger (not thumb), so that special design and manufacture of the structure of the thumb is needed, or special design and manufacture of structures of the proximal knuckle of the thumb and the base knuckle of the thumb; and the difference between the prosthetic thumb and the general prosthetic finger can cause additional workload and processing cost, and the universality of parts is poor, which is not beneficial to reducing the cost.
The thumb has two postures, namely an opposite palm posture and a side palm posture, therefore, a prosthetic thumb needs to make posture rotary motion; however, for a mounting structure used by the existing prosthetic thumb, a lead for connecting a motor is introduced out from a side surface, so that when the prosthetic thumb converts the side palm and opposite palm postures, the lead is pulled, long-term use will cause the lead to be fractured, and in fact, the lead fracture of this kind of prosthetic thumb is a permanent fault.
Because part of the structure of the existing prosthetic thumb has the above problems, the cost of the whole prosthetic finger is high, the prosthetic finger is prone to failure, and the work reliability is poor.
Mounting structures of general prosthetic fingers (the other four prosthetic fingers except the thumb) of some existing prosthetic hands are as follows: the general prosthetic fingers and a finger connector of the prosthetic hand are connected by using finger axial single screws, and when the general fingers unbend, the finger axial single screws and the fingers point to a same direction, so the connection is not reliable, and short-term use will cause loose connection.
Because part of the structure of the existing prosthetic hand has the problems mentioned above, the reliability of the prosthetic hand is poor, and the cost is high.